1. Field of the Invention
This invention relates to a novel ester and halogen containing polyol. More particularly, this invention relates to the preparation of a flame retardant polyol ester and its use in polyurethane and polyester compositions.
2. Description of the Prior Art
Polyurethanes are usually obtained by the reaction of di- or polyisocyanates with polyhydroxy compounds, such as polyethers, polyesters or glycols. The problem of the flammability of these polymer compositions has received considerable attention. A variety of compounds are known that provide satisfactory flame resistance, smoke suppression and self-extinguishing properties when added to polyurethane compositions.
It is known that the polyhydroxy compounds themselves which react with the di- or polyisocyanates can be modified to impart flame retardant properties to the resultant polyurethane composition.
Some prior art methods of forming flame retardant polydroxy compounds, also known as polyols, involve a two step process. A halogen containing anhydride is combined with a polyol to form a half-ester. The half-ester is then reacted with an alkylene oxide to obtain a polyol.
U.S. Pat. No. 3,642,646 discloses polyol compositions useful in preparing rigid foam compositions. These polyols comprise the reaction adducts of polyfunctional aromatic carboxylic acid anhydrides or chlorendic anhydride and polyether polyols. It specifically teaches the use of half esters based on a polyol and tetrabromophthalic anhydride.
U.S. Pat. No. 3,585,185 discloses a process for preparing ester-containing polyols by the reaction of alkylene oxide condensates of organic compounds having at least two active hydrogen atoms with a halogen-containing organic acid anhydride and an alkylene oxide.
U.S. Pat. No. 3,454,530 teaches the use of polyols useful in the preparation of rigid polyurethane foams. These polyols are prepared by the reaction of a di- or tri-alkanolamine with a cyclic anhydride of an organic dicarboxylic acid and a lower alkylene oxide.
Canadian Pat. No. 993,451 discloses halogen-substituted aromatic amide-ester polyols and their use in a flame retardant flexible polyurethane foam.
U.S. Pat. No. 3,676,376 teaches the use of polyester polyols based on tetrabromophthalic anhydride, an aliphatic dicarboxylic acid, a polyol and an aliphatic diol.
U.S. Pat. Nos., 3,565,812, 3,639,541 and 3,639,542 are directed to the preparation of halogen-containing organic acid anhydrides based on ester- and phosphorous-containing polyols.
U.S. Pat. No. 4,264,745 teaches the use of the reaction product of tetrabromophthalic anhydride, dibromoneopentyl glycol and an alkyloxide.
U.S. Pat. No. 3,989,653 teaches the preparation of simple diesters of tetrabromophthalic anhydride comprising the reaction product of tetrabromophthalic anhydride and a polyhydroxy compound containing at least three hydroxyl groups. Example 3 involves the esterification of tetrabromophthalic anhydride and an aromatic diol.
Copending application S-4990 filed herewith claims a normally liquid flame retardant polyol prepared by a process comprising reacting a halogen containing anhydride of a dicarboxylic acid or a mixture of said anhydrides and about 2-10 moles of an aliphatic diol or mixture of diols per mole of said anhydride to obtain a substantially fully esterified halogen containing product in which the acid number does not exceed 10 with the optional removal of unreacted diol during the course of the reacting or subsequent to the reacting.
The novel flame retardant polyol prepared by the process of the present invention has an advantage over the flame retardant polyols found in the prior art. Polyol esters made from halogen containing anhydrides or acids, especially those based on tetrabromophthalic anhydride, have a high viscosity and are difficult to handle by conventional processing methods. Pumps are generally used in the preparation of polyurethane foams. The viscosity of the polyol should preferably by 25,000 cps at 25.degree. C., or lower, to be pumped in a convenient manner. The polyol ester taught by the present invention is liquid and has a low viscosity and is easily handled by conventional processing techniques.
The halogen and ester containing polyols formed by the practice of the present invention are especially useful in the preparation of flame retardant polyurethane compositions. The polyols of the present invention are especially advantageous because they have an average functionality greater than 2. Rigid polyurethane foams prepared using a low functionality polyol have a reduced crosslinked density within their structure. Polyurethane foams prepared by using the higher functionality polyols of the present invention have a higher crosslink density since there are more hydroxy groups per molecule to react with free isocyanate groups. The higher crosslink density is advantageous because this polyurethane foam would have less tendency to melt when exposed to fire and forms a self-supporting insular char which protects the rest of the foam from burning. Higher crosslink density also results in polyurethane foams with better physical properties.